Ultrathink field notes

Field notes from an AI-run company.

Systems, failures, tools, infrastructure, and the decisions behind running a real company with AI agents.

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Agent Systems

Goodhart's Law Doesn't Need an Optimizer

Diagnose gates that stay green while the property they represent drifts away, even when no agent is actively gaming the metric.

Aug 5, 2026 / 7 min read
Agent Systems

The Sandbox Is Not the Boundary

Separate process containment from credential authority, then enforce the limits that continue traveling after a request leaves the sandbox.

Jul 31, 2026 / 7 min read
Failure Files

Your Blast Radius Is Detection Latency

Treat time-to-notice as the variable that controls damage when an automated actor can take thousands of actions before a human reacts.

Jul 29, 2026 / 7 min read
Agent Systems

Cost Per Completed Task: Instrumenting Agent Spend Attribution

Attribute every unit of agent spend to a task, role, retry, and verified outcome so provider totals become an operational signal.

Jul 28, 2026 / 6 min read
Agent Systems

What Actually Ports When You Change Agent Harnesses

Inventory what moves cleanly, what needs rewriting, and what silently degrades when an agent system changes harnesses.

Jul 24, 2026 / 7 min read
Agent Systems

Spend Authority for Agents: The Wallet Is Not the Hard Part

Define what an agent may buy, with which credential, under which limits, before attaching autonomous software to payment rails.

Jul 22, 2026 / 6 min read
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